In recent years, machinery and equipment are developed quickly. Taking CNC machine tool for example, a machining process is executed by CAD/CAM instruction program based on a specification of a workpiece to plan and design a tool profile and machining path, and a control unit of the machine interprets corresponding instruction program, the servo drive outputs the corresponding instruction program in a pulse command manner, an analog voltage manner or a network communication manner, and a servo motor is driven so that a coding signal from an encoder in the servo motor is transmitted back to the servo drive, thus machining the workpiece.
To machine the workpiece efficiently on a single machine with multi-spindles, a multi-spindle control system is developed, and a digital controlling system is employed to control a plurality of servo drives, and each servo drive controls a servo motor on each spindle. However, such a configuration will occupy space and enhance cost. To overcome such a problem, the plurality of servo drives are series connected together by means of a coaxial cable or a fiber optic cable, for instance, a drive is in connection with one of the plurality of servo drives but not a drive is joined with one servo motor, thereby increasing configuration space and cost.
TW Pub. No. I308819 disclosed a triple AC servo drive in which plural power modules and plural control modules are fixed in a module block to supply power toward plural servo motors, thus eliminating repeated parts, such as a communication interface, a display unit, and an input/output unit. Also, a power capacity of an IGBT module on each power module is reduced, and a size of the plural power modules is decreased to save cost, cable arrangement, and installation time. Nevertheless, the plural servo motors in the power module are controlled by matching with plural inverts and plural current sensors, thus increasing a size of each power module. In addition, each inverter is expensive because of its circuit at high current and high power, thus increasing production cost. A brake unit is mounted in each power module to release electric energy when a voltage in USD is high, thereby wasting power consumption.
Thereby, the servo drive is coupled with plural servo motors by increasing the plural power modules, thus enhancing production cost and wasting manufacture time.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.